CN112887251A - Low-complexity PAPR (peak-to-average power ratio) suppression method in OFDM (orthogonal frequency division multiplexing) transmission system - Google Patents

Abstract

The invention discloses a PAPR suppression method with low complexity in an OFDM transmission system, which is to apply a phase factor b in the original partial transmission sequence algorithmⁱThe system is simplified into 1 and-1, so that the complexity of system calculation is greatly reduced; and only 8 times of PAPR calculation is needed, which is far less than 2^8 ^ 256 times of calculation required by the original partial transmission sequence technology, so that the calculation time of the system is greatly reduced, the reliability of phase factor transmission is improved by using BCH coding with error correction capability, and meanwhile, the coded phase factor information is inserted into the pilot frequency position of an OFDM symbol, so that the capability of the system for performing channel estimation by using the pilot frequency is increased.

Description

Low-complexity PAPR (peak-to-average power ratio) suppression method in OFDM (orthogonal frequency division multiplexing) transmission system

Technical Field

The invention relates to the technical field of signal processing, in particular to a method, a system, computer equipment and a storage medium for suppressing PAPR with low complexity in an OFDM transmission system based on a method, a system, the computer equipment and the storage medium for suppressing PAPR with high efficiency, reliability and low complexity in the signal transmission system of an OFDM system.

Background

Ofdm (orthogonal Frequency Division multiplexing), is a kind of multi-carrier modulation. The parallel transmission of high-speed serial data is realized through frequency division multiplexing, and the parallel transmission device has better multipath fading resistance and can support multi-user access. The main idea of OFDM is as follows: the channel is divided into a plurality of orthogonal sub-channels, the high-speed data signal is converted into parallel low-speed sub-data streams, and the parallel low-speed sub-data streams are modulated to be transmitted on each sub-channel. The orthogonal signals can be separated by using correlation techniques at the receiving end, which can reduce mutual interference between the sub-channels.

An OFDM signal consists of a plurality of subcarrier signals that are independently modulated by different modulation symbols. Since the OFDM signal is the sum of many small signals, the phase of these small signals is determined by the data sequence to be transmitted. For some data, these small signals may be in phase and added together in amplitude to produce a large instantaneous peak amplitude. Too large a peak-to-average ratio will increase the complexity of the a/D and D/a and will decrease the efficiency of the rf power amplifier. Since the peak-to-average power ratio (PAPR) of the OFDM system is large and is more sensitive to nonlinear amplification, the OFDM modulation system has a higher requirement on the linear range of the amplifier than the single carrier system.

Disclosure of Invention

In order to solve the technical problems of high complexity, low transmission efficiency and poor reliability of a PAPR suppression algorithm of an OFDM system in the prior art, the invention provides a simplified reliable algorithm based on a partial transmission sequence, which has the advantages of low implementation complexity, high data transmission rate and good system performance, can meet the system index requirements, has low implementation complexity and has the function of channel estimation.

The technical scheme of the invention is as follows: a PAPR restraining method with low complexity in an OFDM transmission system comprises the following steps:

step10, respectively inserting 16 pilot frequencies into N sub-carriers of OFDM symbol at equal intervals in sequence, and dividing N sub-carrier symbols into 8 disjoint sub-blocks XⁱWherein X isⁱ＝X(i:8:N)，i＝1,…,8；

Step20, i equals 1, and each divided subblock XⁱMultiplying by a phase factor b of the response ⁱ1, performing IFFT, calculating to obtain a PAPR value, and setting the PAPR value as PAPR _ min;

step30, let i equal i +1, so that i equals 2, update b²Repeating the process of Step20 and calculating a new PAPR value when the PAPR value is-1;

step40, New PAPR calculated if Step30>PAPR _ min, then phase factor bⁱWhen the PAPR is 1(i is 1, …,8), the PAPR is kept unchanged, otherwise, the PAPR is updated to new PAPR _ min, and the phase factor b corresponding to i is 2 is updated²Is-1, the rest bⁱKeeping the same;

step50, repeat Step30, if i +1 < 8, update bⁱRepeating the subsequent steps of Step30, and performing PAPR value comparison and phase factor b of Step40ⁱUpdating; otherwise, the optimal phase factor b is obtainedⁱAnd exits the PAPR minimum calculation procedure, thus obtaining bⁱ(i-1, …,8) sequence, bⁱIn (b)¹The value is fixed to be 1, and the other 7 bits are selected from (1, -1) according to the calculation result;

step60, b obtained finallyⁱ(i ═ 1, …,8) in the last 7 bits, with 1 mapped to 1 and-1 mapped to 0; BCH (15,7) coding is carried out, and a 15-bit 0, 1 sequence is obtained after coding;

step70, mapping the coded 15-bit 0, 1 sequence in Step60 to 1 according to 1, mapping the 1-1 to 0, and placing the 15-bit 1-1 sequence 15 bits after the pilot inserted in Step10, thereby obtaining an OFDM symbol with full PAPR suppression and channel estimation capability.

Preferably, the pilot has a value of 1.

Preferably, the sub-block XⁱThe positions in the corresponding number sequence X are:

X¹＝X(1,9,17,…,N-7)，X²＝X(2,10,18,…,N-6)，

X³＝X(3,11,19,…,N-5)，X⁴＝X(4,12,20,…,N-4)，

X⁵＝X(5,13,21,…,N-3)，X⁶＝X(6,14,22,…,N-2)，

X⁷＝X(7,15,23,…,N-1)，X⁸＝X(8,16,24,…,N)。

preferably, the calculation process of the PAPR value is:

step21, and sub-block X in Step20ⁱMultiplying by a phase factor b of the responseⁱIFFT is carried out on the obtained product 1 to obtain

Wherein x represents xⁱA series of combinations of (1), xⁱIs XⁱInverse fourier transform (IFFT) results of (a);

step22, calculating to obtain the corresponding PAPR value by the formula PAPR ═ E { max (x ^2)/E (x ^2) }, wherein E { } represents the average value.

Compared with the prior art, the invention has the following beneficial effects:

1. the invention uses the phase factor b in the original part transmission sequence algorithmⁱThe system is simplified into 1 and-1, so that the complexity of system calculation is greatly reduced;

2. in the invention, the PAPR calculation only needs 8 times, which is far less than 2^8 ^ 256 times of calculation required by the original partial transmission sequence technology, thereby greatly reducing the calculation time of the system.

3. The invention uses BCH coding with error correction capability, improves the reliability of phase factor transmission, and inserts the coded phase factor information into the pilot frequency position of OFDM symbol, thus increasing the capability of the system for channel estimation by using pilot frequency.

Drawings

FIG. 1 is a diagram of pilot insertion locations in accordance with the present invention;

FIG. 2 is a flow chart of the algorithm calculation of the present invention;

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be understood that the terms "front", "back", "left", "right", "up", "down", and the like indicate orientations or positional relationships based on those shown in the drawings, and are used merely for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the devices or elements indicated by the terms must have specific orientations, be constructed and operated in specific orientations, and therefore, should not be construed as limiting the present invention.

The invention provides the following technical scheme, the calculation process of the main algorithm calculation is shown as the attached figure 2, and the corresponding step process is as follows:

1. dividing N (the number of common OFDM subcarriers is integral multiple of 16) subcarriers of one OFDM symbol into 8 disjoint sub-blocks; wherein, 16 pilot values 1 have been inserted into N subcarriers at equal intervals in sequence, and the pilot positions are as shown in fig. 1.

Then divide the N sub-carrier symbols into 8 disjoint sub-blocks:

D＝[X¹,X²,…,X⁸] (1)

wherein D is the collection of sub-blocks, XⁱIs the ith sub-block with continuous distribution and same size corresponding to the original sequence XⁱX (i:8: N), i-1, …,8, pairs of subblocksThe positions in the strain column X are:

X¹＝X(1,9,17,…,N-7)，X²＝X(2,10,18,…,N-6)

X³＝X(3,11,19,…,N-5)，X⁴＝X(4,12,20,…,N-4)

X⁵＝X(5,13,21,…,N-3)，X⁶＝X(6,14,22,…,N-2)

X⁷＝X(7,15,23,…,N-1)，X⁸＝X(8,16,24,…,N)

2. dividing 8 sub-blocks XⁱI is 1, …,8, multiplied by 1, respectively, i is: each partitioned sub-block is multiplied by a phase factor b of the responseⁱ1(i ═ 1, …,8), followed by an IFFT (inverse fast fourier transform), yields:

PAPR＝E{max(x^2)/E(x^2)} (3)

wherein x represents xⁱA series of combinations of (1), xⁱIs XⁱInverse fourier transform (IFFT) results of (a); wherein E { } denotes an average value; PAPR is expressed as peak-to-average power ratio;

the PAPR value of equation (2) is calculated by equation (3) and set as PAPR _ min.

3. Let i equal 2, update b²When the PAPR is-1, the PAPR value of equation (2) is recalculated.

4. If the calculated PAPR in step3 is the same as the PAPR>PAPR _ min, then phase factor bⁱ1(i 1, …,8), left unchanged; otherwise, updating PAPR _ min to be the current PAPR value, and updating the phase factor b corresponding to i-2²Is-1, the rest bⁱRemain unchanged.

5. If i +1 < 8, update bⁱRepeating the step3 when the PAPR value is-1, and then carrying out PAPR value comparison and phase factor updating in the step 4; otherwise, obtaining the optimal phase factor bⁱAnd then exits the PAPR minimum calculation procedure. At this time, b is obtainedⁱ(i-1, …,8) sequence, bⁱIn (b)¹Fixed to a value of 1, the remaining 7 bits being based on the calculationSelecting between (1, -1).

6. B to be finally obtainedⁱ(i ═ 1, …,8) in the last 7 bits, with 1 mapped to 1 and-1 mapped to 0; BCH (15,7) coding is carried out, and a 0, 1 sequence with 15 bits is obtained after coding. Similarly, a 15-bit 1, -1 sequence is placed into the last 15 bits of the pilot positions shown in fig. 1 according to the rule that 1 maps to 1, -1 maps to 0. Finally, an OFDM symbol with complete PAPR suppression and channel estimation capability is obtained.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (4)

1. A method for suppressing PAPR with low complexity in an OFDM transmission system is characterized by comprising the following steps:

step10, respectively inserting 16 pilot frequencies into N sub-carriers of OFDM symbol at equal intervals in sequence, and dividing N sub-carrier symbols into 8 disjoint sub-blocks XⁱWherein X isⁱ＝X(i:8:N)，i＝1,…,8；

Step20, i equals 1, and each divided subblock XⁱMultiplying by a phase factor b of the responseⁱ1, performing IFFT, calculating to obtain a PAPR value, and setting the PAPR value as PAPR _ min;

step30, let i equal i +1, so that i equals 2, update b²Repeating the process of Step20 and calculating a new PAPR value when the PAPR value is-1;

step40, New PAPR calculated if Step30>PAPR _ min, then phase factor bⁱWhen the PAPR is 1(i is 1, …,8), the PAPR is kept unchanged, otherwise, the PAPR is updated to new PAPR _ min, and the phase factor b corresponding to i is 2 is updated²Is-1, the rest bⁱKeeping the same;

step50, repeat Step30, if i +1 < 8, update bⁱRepeating the subsequent steps of Step30, and performing PAPR value comparison and phase factor b of Step40ⁱUpdating; otherwise, get the bestPhase factor bⁱAnd exits the PAPR minimum calculation procedure, thus obtaining bⁱ(i-1, …,8) sequence, bⁱIn (b)¹The value is fixed to be 1, and the other 7 bits are selected from (1, -1) according to the calculation result;

step60, b obtained finallyⁱ(i ═ 1, …,8) in the last 7 bits, with 1 mapped to 1 and-1 mapped to 0; BCH (15,7) coding is carried out, and a 15-bit 0, 1 sequence is obtained after coding;

step70, mapping the coded 15-bit 0, 1 sequence in Step60 to 1 according to 1, mapping the 1-1 to 0, and placing the 15-bit 1-1 sequence 15 bits after the pilot inserted in Step10, thereby obtaining an OFDM symbol with full PAPR suppression and channel estimation capability.

2. The method as claimed in claim 1, wherein the pilot has a value of 1.

3. The method according to claim 1, wherein the sub-block X is used for PAPR suppression with low complexity in the OFDM transmission systemⁱThe positions in the corresponding number sequence X are:

X¹＝X(1,9,17,…,N-7)，X²＝X(2,10,18,…,N-6)，

X³＝X(3,11,19,…,N-5)，X⁴＝X(4,12,20,…,N-4)，

X⁵＝X(5,13,21,…,N-3)，X⁶＝X(6,14,22,…,N-2)，

X⁷＝X(7,15,23,…,N-1)，X⁸＝X(8,16,24,…,N)。

4. the method according to claim 3, wherein the PAPR value is calculated by:

step21, and sub-block X in Step20ⁱMultiplying by a phase factor b of the responseⁱIFFT is carried out on the obtained product 1 to obtain

Wherein x represents xⁱA series of combinations of (1), xⁱIs XⁱInverse fourier transform (IFFT) results of (a);

step22, calculating to obtain the corresponding PAPR value by the formula PAPR ═ E { max (x ^2)/E (x ^2) }, wherein E { } represents the average value.

Images